Flux for the smelting and refining of magnesium and magnesium alloys



Patented Jan. 29, 1935 rLUx FOR. rm: sMnL'rmG arm nnrmma F MAGNESIUM AND MAGNESIUM AL- LOYS Alexander Luschenowsky, Berlin, Germany No Drawing. Application July 21, 1933, Serial a... 681,559. In Germany July 29, 1932 comma. (01. 15-1) I have'filed an application in Germany on the 29th July, 1932. a

In the smelting of magnesium and of magnesuim alloys in open crucibles the magnesium forms chemical, combinations with oxygen and nitrogen. In order to deter the formation of these undesirable compounds'and in order to reduce the impurities and oxides already present in the raw material fluxes are used. The hitherto known fluxes were applied to the surface of the molten metal in a thick layer. The specific gravity of the known fluxes was always made higher than that of the molten metal. For the purpose of mixing the fluxes with the liquid metal it was always necessary to stir very thoroughly. whereupon finally the surface was covered once again with the same flux. The'said known fluxes have the disadvantage-that in spite of along period of refinement and in spite of the high temperature which was necessary, a considerable quantity of magnesium oxides as also nitrides and chlorides was always presentin the cast material. In order to ensure the resistive properties of magnesium and its alloys to chemical attack (corrosion) as also to ensure good mechanical properties, the elimination of magnesium oxides'as also metallic chorides and nitrides is of the greatest importance inasmuch as the said impurities lead to rapid disintegration, for example on contact with water. The necessity when employing the hitherto known fluxes, of providing 'for energetic mixing or agitation of the contents of the crucible during the refining operation in order to avoid the rapid separation of the flux from the metal leads'to a simultaneous oxidation of the metalas a result of its very considerable contact with the air.

Moreover, the long period of heating which is necessary assists the formation of undesired combinations ofthe magnesium with constituents of the flux.

The flux for the smelting. and refining of magnesium and magnesium alloys forming the subject matter of the present invention, is free from 45 the above mentioned disadvantages and ensures a rapid and complete removal from the metal of oxides and other impurities and detrimental substances, particularly metallic chlorides. The continuous agitation of the molten material is 50 also no longer necessary.

According to the invention it is proposed. to use as a flux a mixture which in addition to halogen' compounds such as magnesium chloride, and if desired alkali halogen compounds, contains man-' 5 ganese compounds having an oxygen content,

particularly manganese oxide MmO: or manganese dioxide MnOz.

The flux made up according to the invention has the advantage that the oxygen compounds of manganese contained therein, which are not 5 very stable, free the molten mass from undesired substances, particularly chlorides, in a very reliable manner. 7,

The flux described may. for example, be produced by mixing together the following constituents:

- Parts by weight Magnesium chloride 21to38 Potassium chloride Ste '9 Sodium fluoride .5to 3 Calcium fluoride .5to 3 Manganese oxide MmO: or manganese dioxide MnOz or both together .2 to 10 In order to obtain an increased action on the molten material the specific gravity of the flux in the molten condition, according to the invention, is preferably chosen so that it closely approximates to the specific gravity of the molten metal. 7 This result is attained by suitable choice or the number 25 of parts by weight of the individual constituents of the flux within the above-named limits, in such manner as to give a result corresponding to the specific gravity of the molten metal in each particular case. The best results are obtained if the .30

flux is distributed on the bottom of the crucible and the pieces of metal are then laid upon the The close proximity of the specific gravities of the flux and of the metal to be refined when they a5 are. both in the molten condition renders agita tion during the refining operation for the 9 E 0 of mixing, entirely unnecessary. The temperature differences in the upper and lower part of.

the crucible suflice to maintain entirely auto- 40 and its alloys with the flux described may advan- I tageously be effected somewhat in the following manner:

The flux is shaken on to the bottom of the crucible. This measure protects the metal from being overheated, inasmuchas the flux is abad conductor of heat. The metal to be smelted and refined is placed on the layer of fiux. The more closely the specific gravity of the flux has been made to approximate to that 01' the metal to be refined when in the molten condition, the better is the mixing of the metal with the fiux after both of them have been melted. By the reduction 01' the oxides the flux acquires a higher specific ravity. The flux which has been used consequently sinks down whilst the unused flux surrounds the metal on all sides. All the impurities collect on the bottom of the crucible.

After the whole of the metal in the crucible has been melted it is refined in a very short time (with small crucibles a period of about l5 to 20 minutes is sufllcient) and is separated from the fiux. The metal can now be poured into the moulds. If, however, the metal refined with the above-described fiux is allowed to solidify in the crucible it takes up the form of a regulus surrounded on all sides by the flux.

No particular precautionary measures are necessary in the refining process and the impurities contained in the metal, particularly mag-' nesium oxides and chlorides, are successfully removed.

The very diflicult cleaning 01' the crucible which was unavoidable with the hithertoknown fluxes is entirely avoided, inasmuch as no adhesive deposits remain on the walls of the crucible. The metal is poured out up to the last drop.

The removal of the said impurities, particularly chlorides, by means of the flux results in a substantial increase of the resistance to corrosion and of the mechanical properties, for example the tensile'strength and expansion of the magnesium and its alloys.

I claim:

1. A fiux for the smelting and refining of magnesium and magnesium alloys, consisting of a mixture comprising halogen, compounds of magnesium, and manganese compounds having an oxygen content.

2. A fiux for the smelting and refining of magnesium and magnesium alloys, consisting 01' a mixture comprising halogen compounds of magnesium, alkali halogen compounds, and manganese compounds having an oxygen content.

, 3. A fiux for the smelting and refining of magnesium and magnesium alloys, consisting or a 7 mixture comprising halogen compounds of magnesium, and manganese dioxide (MnOz) 4. A flux for the smelting'and refining of magnesium and magnesium alloys, consisting of a mixture comprising halogen compounds 01 magnesium, alkali halogen compounds, and manganese dioxide (M1102) and manganese oxide (M11203) 5. A fiux for the smelting and refining of magnesium and magnesium alloys, consisting of a mixture comprising halogen compounds of magnesium, and manganese compounds having an oxygen content, said flux having a specific gravity in the molten condition approximating as closely as possible to the specific gravity of the molten magnesium or magnesium alloy.

6. A fiux for the smelting and refining of magnesium and magnesium alloys, consisting of a mixture comprising halogen compounds of magnesium, alkali halogen compounds, and manganese compounds having an oxygen content, said flux having a specific gravity in the molten condition approximating as closelyas possible to the specific gravity of the molten magnesium or magnesium alloy.

7. A flux for the smelting and refining of magnesium and magnesium alloys, consisting of a mixture comprising 21 to 38 parts by weight of magnesium chloride, 6 to 9 parts by weight of potassium chloride, .5 to 3 parts by weight of sodium fluoride, .5 to 3 parts by weight of calcium fiuoride, and .2 to 10 parts by weight of man ganese dioxide (M1102) said flux having a specific gravity in the molten condition closely approximating to the specific gravity ofthe molten magnesium or magnesium alloy. v

8. A flux for the smelting and refining of magnesium and magnesium alloys, consisting of a mixture comprising 2l to 38 parts by weight of magnesium chloride, 6 to 9 parts by weight of potassium chloride, .5 to 3 parts by weight of sodium fluoride, .5 to 3 parts by weight of calcium fluoride, and .2 to 10 parts by weight 01' manganese dioxide (MnO-z) and manganese oxide (MnzOa) said flux having a specific gravity in the molten condition closely approximating to the specific gravity of the molten magnesium or magnesium alloy.

ALEXANDER LUSCHENOWSKY. 

